Airbag device for front passenger&#39;s seat

ABSTRACT

The airbag device for front passenger&#39;s seat is mounted on the dashboard in front of the front passenger&#39;s seat. The airbag device for front passenger&#39;s seat includes an airbag to be inflated with the inflation gas, and an inflator for feeding the airbag with the inflation gas of pyro- and long mass flow type. The gas permeability rate of the airbag is 1.0 l/cm 2 /min or under at 20 kPa air pressure, and its weight is 230 g/m 2  or under. This airbag device for front passenger&#39;s seat prevents the gas leakage, expands and inflates the airbag properly, and constitutes to the weight reduction.

The present application claims priority to Japanese Patent Applicationof Okada et al., filed May 31, 2002, under No. 2002-160200, and JapanesePatent Application of Tajima et al., filed May 31, 2002, under No.2002-160224, the entirety of each is hereby incorporated into thepresent application by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an airbag device for front passenger'sseat to be mounted on the instrument panel (as will be called“dashboard” hereinafter) in front of a front passenger's seat.

2. Description of Related Art

Conventionally, an airbag device for front passenger's seat includes anairbag, an inflator for supplying the airbag with inflation gas, a casefor holding the airbag and the inflator, and an airbag cover forcovering the folded airbag.

As an inflator, a disc-type is used, for example, as disclosed inJapanese Patent Laid-Open No. Hei 9-86319. This disc-type inflatorincludes a cylindrical body and a flange projected from the outercircumference of the body for the attachment to the case. The body isprovided on the upper outer surface above the flange with a plurality ofgas discharge ports for discharging the inflation gas.

The case has a bottom wall with an insert hole large enough to insertthe upper portion of the inflator with the gas discharge ports thereintoward the inner space of the case.

The airbag has an opening for admitting the inflation gas. The airbag issecured to the bottom wall of the case by means of an annular retainer,which is pressed on the periphery of the opening and attached to thebottom wall of the case.

Moreover, the inflator in the above disclosure is a pyro-type whichgenerates inflation gas by chemical reaction such as burning reaction ofgas generating material. The pyro-type inflator is favorably used for avehicle because of its compactness, compared with a hybrid type inflatorcharged with inflation gas.

However, the conventional pyro-type inflator has a room for improvementin the timing of supplying the inflation gas to the airbag for frontpassenger's seat.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an airbag device forfront passenger's seat securing a proper expansion and inflation of theairbag.

The first airbag device for front passenger's seat of the presentinvention is mounted on the dashboard in front of the front passenger'sseat.

The first airbag device for front passenger's seat of the presentinvention includes an airbag to be inflated with inflation gas, and aninflator of pyro-type and long mass flow type, for supplying the airbagwith the inflation gas. The gas permeability rate per unit area of theairbag is 1.0 l/cm²/min or under at 20 kPa air pressure, and the weightof the airbag is 230 g/m² or under.

In the first airbag device for front passenger's seat of the presentinvention, the inflator for supplying the airbag with inflation gas is apyro-type, which generates the inflation gas by chemical reaction, and along mass flow type.

In this inflator of long mass flow type, the amount of gas dischargedinto the airbag increases from when the reaction force against thepassenger is most required upon the inflation of the airbag on, i.e.,from 30 msec after ignition of the inflator on, in comparison with aconventional type.

The long mass type inflator, more specifically, is an inflator whosemass flow curve area from 30 msec after ignition on occupies more thanabout 25% of the entire area of a mass flow curve. In other words, it isan inflator whose area from 20 msec after ignition on occupies more thanabout 45% of the entire area of the mass flow curve. In yet anotherwords, it is an inflator whose area before the peak time against theentire area of the mass flow curve is less than about 55%. In stillanother words, it is an inflator whose mass flow curve peaks out atabout 15 to 35 msec after ignition.

The mass flow curve indicates the relationship between the amount of gasdischarged from the inflator per unit time and the time, and it iscalculated from a tank curve data obtained from the tank combustiontest.

The tank combustion test is conducted as follows:

Fix the inflator in a stainless-steel tank whose internal volume is 60l. Close the tank tightly in room temperature, and connect the inflatorto an outside electric ignition. Then measure the pressure change in thetank for the duration of 0 to 200 msecs, the ignition time being 0, by apressure transducer equipped in the tank. The measured data iscomputer-processed to resultingly obtain a tank pressure versus timecurve for evaluating the performance of the inflator, which is a tankcurve. This tank curve, or the tank pressure versus time curve, isintegrated and converted into a gas generation rate per time, so thatthe mass flow curve is calculated.

The area from 30 msec after ignition on occupying more than about 25% ofthe entire area of the mass flow curve means that the total of mass flowarea from 30 msec after ignition to the timing of the mass flow'sdecreasing to zero in a curve indicating the change of the gas amountper unit time in the course of time is more than about 25% of the entirearea of the mass flow curve. The inflator of this type generates morethan about 25% of the total amount of gas generation in the timing whenthe airbag for front passenger's seat inflated requires the greatestreaction force against the passenger, i.e., from 30 msec after ignitionon. Therefore, the airbag is able to protect the passenger properly.Here, in a dual type inflator having two combustion chambers, the timingof 30 msec has its importance in burning gas generating agent in thefirst combustion chamber where the combustion takes place firstly.Moreover, the area from 30 msec after ignition on desirably occupiesabout 35% or more, or further desirably, about 45% or more of the entirearea of the mass flow curve.

The area from 20 msec after ignition on occupying more than about 45% ofthe entire area of the mass flow curve means that the total of mass flowarea from 20 msec after ignition to the timing of the mass flow'sdecreasing to zero in a curve indicating the change of the gas amountper unit time in the course of time is more than about 45% of the entirearea of the mass flow curve. The inflator of this type generates morethan about 45% of the total amount of gas generation in the timing whenthe airbag for front passenger's seat inflated requires the reactionforce against the passenger, i.e., from 20 msec after ignition on.Therefore, the airbag is able to protect the passenger properly. Here,the timing of 20 msec has its importance in an inflator with a singlecombustion chamber, or in a dual-type inflator having two combustionchambers when burning gas generating agent in both chambers at the sametime. Moreover, the area from 20 msec after ignition on desirablyoccupies about 55% or more of the entire area of the mass flow curve.

The area before the peak time against the entire area of the mass flowcurve being less than about 55% means that the total of mass flow areafrom the ignition to the peak time of the mass flow in a curveindicating the change of the gas amount per unit time in the course oftime is less than about 55% of the entire area of the mass flow curve.The inflator of this type is able to suppress the amount of the gasgenerated before the peak time of the mass flow less than about 55% ofthe entire amount, thereby to supply the least gas necessary in theinitial stage of the expansion of the airbag, and to supply more gas tothe airbag after the peak time. Therefore, the airbag is able to protectthe passenger properly. The area before the peak time is desirably about40% or less of the entire area of the mass flow curve in an inflatorwith a single combustion chamber, or in a dual-type inflator whenburning gas generating agent at the same time in both chambers. It isdesirably about 50% or less in a dual type inflator when burning gasgenerating agent in a combustion chamber where the combustion takesplace firstly.

Moreover, the mass flow curve's peaking out at about 15 to 35 msec afterignition means that the peak time period of the gas amount is within therange of about 15 to 35 msec after ignition in the curve indicating thechange of the gas amount per unit time in the course of time. Theinflator of this type is able to supply the airbag with more gas nearthe timing when the airbag needs to apply the greatest reaction forceagainst the passenger, i.e., from 30 msec after ignition on. Therefore,the airbag is able to protect the passenger properly. The peak time ofthe mass flow curve is desirably within the range of about 16 to 24 msecafter ignition, in an inflator with a single combustion chamber, or in adual-type inflator when burning gas generating agent at the same time inboth chambers. It is desirably within the range of about 25 to 30 msecafter ignition in a dual type inflator when burning gas generating agentin a combustion chamber where the combustion takes place firstly.

When the inflation gas from the inflator of this long mass flow type isintroduced into the airbag for front passenger's seat, the amount of theinflation gas discharged increases from 30 msec after ignition on, ormore desirably, from 30 to 60 msec after ignition, in comparison with aconventional inflator. Therefore, the passenger in the front passenger'sseat is properly protected.

In the first airbag device for front passenger's seat of the presentinvention, therefore, the inflator is made compact, and is able toproperly expand the airbag since it employs an inflator of pyro-type andlong mass flow type.

If the inflation gas leaks from the airbag, however, the meaning ofemploying the long mass flow type inflator is decreased.

To cope with this problem, it is conceivable to provide a coating layerof silicon or the like on the inner surface of the airbag to prevent gasleakage. However, it increases the manufacturing steps of the airbag andits cost, and the weight of the airbag as well, which goes against theweight-saving of the parts mounted on the vehicle.

In the airbag device for front passenger's seat of the presentinvention, however, the gas permeability rate is 1.0 l/cm²/min or underat 20 kPa air pressure. In the present invention, therefore, the leakageof the inflation gas from the airbag is prevented, so that it ispossible to make the most use of the characteristic property of the longmass flow type inflator. As a result, the present invention is able toprovide the smooth inflation state of the airbag.

Since the weight of the airbag is less than 230 g/m², moreover, itcontributes to the weight reduction of the airbag. The airbag withinthis weight range includes the following airbags, for example: an airbagformed by base cloths woven of heavy thick thread or light fine thread,without a coating layer, or an airbag formed by base cloths woven oflight fine thread with a thin coating layer.

Moreover, the long mass flow inflator itself is able to contribute tothe weight reduction of the airbag by reducing the discharge amount ofthe inflation gas, since the gas permeability rate of the airbag is low.

In the airbag device for front passenger's seat of the presentinvention, therefore, it is able to secure the smooth expansion andinflation of the airbag even if employing an inflator of long mass flowtype, and to realize the weight reduction.

It is desired that the gas discharge rate of the inflator per unitvolume of the airbag completely inflated be 0.026 mol/l or under. Theinflator like this is lighter than a conventional pyro-type inflatorwhose discharge rate per unit volume is 0.029 to 0.032 mol/l, andthereby to contribute to the weight reduction of the airbag device. Ofcourse, the smooth expansion and inflation of the airbag is not hinderedeven with a compact inflator like this, since the gas leakage from theairbag does not occur. Here, the discharge rate of the inflator per unitvolume of the airbag is desirably 0.02 mol/l or more, in the light ofsecuring the internal pressure of the airbag.

Moreover, if the airbag device is so constructed that the headdeceleration of the unbelted passenger dummy in the frontal collisionFRB test according to FMVSS No. 208-66FR65403, effective on May 28,2003, may be 100 m/s² or over, it is desirable with respect to therestraint performance of the airbag for the front passenger's seat.

In this case, the airbag is desirably constructed as follows:

the airbag includes an inlet port for admitting the inflation gas, andis folded and housed in a case, and pushes and opens the doors arrangedin the instrument panel upon the inflow of the inflation gas from thegas inlet port to expand and inflate toward the vehicle's rear side. Asthe shape completely expanded and inflated, the airbag includes apassenger's side wall to be arranged generally along the verticaldirection and closer to the passenger, and a side wall portion extendedtoward the vehicle's front side from the outer peripheral edge of thepassenger's side wall while narrowing in a generally conical shape. Theairbag is further provided at the front lower side of the side wallportion as completely inflated with the gas inlet port arrangedgenerally horizontally, and the peripheral edge of the gas inlet port isattached to the case. The airbag is housed in the case after beingfolded through the preliminary folding step firstly, and then throughthe transverse folding step and vertical folding step. The preliminarilyfolded shape of the airbag is flat with the part near the upper edge ofthe passenger's side wall disposed in a position confronting the gasinlet port, and with the passenger's side wall overlapped with the lowerpart of the side wall portion as inflated.

With this construction, when the airbag expands and inflates, the airbaglets the inflation gas in from the gas inlet port, and expands andinflates while unfolding transversely and vertically. At this time, thepart near the upper edge of the passenger's side wall confronting thegas inlet port is pushed up intensely by the pressure of the initialinflation gas flowing in, prior to other part of the passenger's sidewall such as the lower part, since the part is disposed to confront thegas inlet port in the preliminary folding. This helps the passenger'sside wall to be deployed generally along the vertical direction.

Moreover, if the part near the upper edge of the passenger's side wallis pushed up intensely, the transverse and vertical folding is unfoldedquickly. This helps the passenger's side wall to be expanded widely.

Consequently, the passenger's side wall disposed generallyperpendicularly to the gas inlet port peripheral edge is quicklydeployed generally along the vertical direction when the airbag expandsand inflates, and the airbag is widely expanded so as not to apply apartial pressure to the passenger. With this construction, accordingly,the head deceleration of 100 m/s² or over is easily obtained in theaforementioned frontal collision FRB test.

When the preliminary folding of the airbag is completed, the generallyentire area of the passenger's side wall is desirably flatly expandedwhile the side wall portion is folded. When the airbag expands andinflates, with this construction, the passenger's side wall is easilymoved toward the passenger in a state widely expanded transversely andvertically, compared with the case in which the passenger's side wall isalso folded. Therefore, it is able to suppress the speed of thepassenger's side wall moving toward the passenger, and to obtain thehead deceleration of 100 m/s² or over more easily in the frontalcollision FRB test. Moreover, the preliminary folding of the aboveairbag can be done only by folding the side wall portion while leavingthe generally entire area of the passenger's side wall flatly expanded,thereby facilitating the preliminary folding work.

When the preliminary folding of the airbag is over, it is desired thatthe upper part of the gas inlet port in the side wall portion is foldedand disposed in the range from the vicinity of the rear edge of the gasinlet port toward the front side.

In the preliminary folding, the upper part of the gas inlet port in theside wall portion can be folded and disposed in the front side of thefront edge or the rear edge of the gas inlet port, or folded anddisposed over the gas inlet port. However, if the upper part of the gasinlet port in the side wall portion is folded between the gas inlet portand the upper part of the passenger's side wall and disposed in therange from the vicinity of the rear edge of the gas inlet port towardthe front side, the following working-effects are obtained.

Specifically, the upper part of the gas inlet port in the side wallportion is folded and disposed in the range from the vicinity of therear edge of the gas inlet port toward the front side, and not extendedto the far rear side of the gas inlet port. Accordingly, when theinflation gas is introduced from the gas inlet port, the part near theupper edge of the passenger's side wall is pushed up with the upper partof the gas inlet port in the side wall portion interposed, and the upperpart of the gas inlet port in the side wall portion itself also ispushed up. At this time, the upper part of the gas inlet port in theside wall portion is released from the gas inlet port while beingunfolded. As a result, the part near the upper edge of the passenger'sside wall comes to confront the gas inlet port directly, and helps thepassenger's side wall to be disposed generally vertically. Therefore,with this construction, the action of deploying the passenger's sidewall generally vertically quickly is not hindered even if the upper partof the gas inlet port in the side wall portion is interposed between thegas inlet port and the part near the upper edge of the passenger's sidewall. Of course, if the upper part of the gas inlet port in the sidewall portion is folded at the front side of the rear edge of the gasinlet port, the passenger's side wall is more quickly deployed generallyalong the vertical direction. Furthermore, if the upper part of the gasinlet port in the side wall portion is folded at the front side of thefront edge of the gas inlet port, the passenger's side wall is even morequickly deployed generally along the vertical direction.

The airbag may be provided with a commutator cloth for receiving theinflation gas flowing out of the dashboard and changing the gas flowdirection at the position within the airbag and out of the dashboard,when the airbag inflates admitting the inflation gas. With thisconstruction, when the airbag device is put in action, the inflation gasflowing into the airbag is changed in its course by the commutator clothat the position out of the dashboard, and therefore, the inflation gasis prevented from abutting directly against the inner surface of theairbag. In other words, the inflation gas does not straightly abut theinner surface of the base cloths constituting the bag shape of theairbag, which is protruded from the dashboard, in a direction in whichthe inflation gas initially flows into the airbag. Therefore, the damageto the base cloths constituting the airbag is reduced, and the gasleakage from the airbag is prevented. As a result, the gas permeabilityof the airbag mounted on the vehicle is further lowered, therebypromoting the expansion and inflation of the airbag.

The second airbag device for front passenger's seat according to thepresent invention is mounted on the dashboard in front of the frontpassenger's seat. This airbag device includes: an airbag having anopening for admitting the inflation gas; an inflator of a long mass flowtype generating the inflation gas by chemical reaction, and of a disctype, which is provided on the outer circumference of the end portionwith a plurality of gas discharge ports for discharging the inflationgas; a case for holding and housing the airbag folded and holding theinflator; and an annular retainer for attaching the airbag to the caseby holding the opening peripheral edge of the airbag. The case includesa bottom wall with an insert hole from which the end portion of theinflator having the gas discharge ports is inserted therein. Theretainer includes: an annular base attached to the periphery of theinsert hole of the case bottom wall while pressing the peripheral edgeof the airbag opening onto the periphery of the insert hole of thebottom wall; and a cover wall extended from the base so as to block thepart of the airbag neighboring the opening peripheral edge held by thebase from the gas discharge ports of the inflator. The mist contained inthe inflation gas discharged from the gas discharge ports adheres on thecover wall, and the cover wall includes a mist growth prevention meansto prevent the mist from forming mist agglomerates.

The second airbag device for front passenger's seat according to thepresent invention employs an inflator of pyro-type, which generatesinflation gas by chemical reaction, and of long mass flow type, as theinflator for supplying the airbag with the inflation gas, as in thefirst embodiment. Accordingly, the inflator is compact, and is able toexpand and inflate the airbag for front passenger's seat properly.

Here, since a pyro- and long mass flow type inflator acts gently, theinflation gas contains a lot of mist. Although most of the mist diffusesand is cooled off immediately upon the inflation of the airbag, some ofthe mist adheres to the retainer located around the gas discharge ports.This mist is likely to stick together with the following mist and formmist agglomerates. In this case, the mist inside a mist agglomerate isdifficult to be cooled off, and therefore, it takes a certain time forthe whole mist agglomerate to be cooled off.

In the second airbag device for front passenger's seat according to thepresent invention, however, even if the mist contained in the inflationgas is discharged from the gas discharge ports, it adheres to the coverwall. The mist is prevented from forming great mist agglomerates by themist growth prevention means.

In the second airbag device for front passenger's seat according to thepresent invention, therefore, even if the inflation gas discharged fromthe inflator of long mass flow type contains a lot of mist, the mistdoes not form great mist agglomerates.

Moreover, since the cover wall of the retainer is arranged so as toblock the part of the airbag neighboring the opening peripheral edgeheld by the base from the gas discharge ports of the inflator, itprevents the high temperature gas containing the high temperature mistfrom hitting the part of the airbag neighboring the opening peripheraledge directly, and contributes to the protection of the part of theairbag neighboring the opening peripheral edge from heat.

The mist growth prevention means may be constructed, for example, byforming the cover wall of the retainer in a generally square cylindricalshape encircling the end portion of the inflator with the gas dischargeports, and providing the cover wall with through portions penetratingthe cover wall at the four corners thereof.

If the cover wall has a generally square cylindrical shape encirclingthe inflator, the mist is likely to gather to form mist agglomerates atthe four corners. With the above construction, however, even if the mistgathers in the corners, it is blown off the through portions beforeforming agglomerates, and does not form big mist agglomerates.

The width of the through portion is desirably 5 to 15 mm, and the lengthis desirably 10 to 15 mm. If the width is under 5 mm, it is difficultfor the mist to go out of the cover wall, and if it is over 15 mm, it isdifficult for the mist to adhere to the cover wall. If the length isunder 10 mm, it is difficult for the mist to go out of the cover wall,and if it is over 15 mm, it is difficult for the mist to adhere to thecover wall.

The mist growth prevention means maybe provided by forming numbers ofthrough holes in the cover wall of the retainer. With this construction,the mist from the gas discharge ports goes out of the through holesbefore growing, or adheres to the peripheral edge of the through holesin the cover wall. The mist adhered to the peripheral edge of thethrough holes is prevented from forming mist agglomerates since the mistcontinues to flow out of the through holes and little mist follows toadhere thereto.

Even if it grows to form mist agglomerates, the agglomerates are likelyto adhere to the inner circumference of the through holes which aregreat in number, and the agglomerates are hardly blown off into theairbag.

The internal diameter of the through holes is desirably 1 to 3 mm, andthe pitch of forming the through holes is desirably 5 to 10 mm. If theinternal diameter is under 1 mm, it is difficult for the mist to go outof the cover wall, and if it is over 3 mm, it is difficult for the mistto adhere to the cover wall. If the pitch is under 5 mm, it is difficultfor the mist to adhere to the cover wall, and if it is over 10 mm, it isdifficult for the mist to go out of the cover wall.

The mist growth prevention means may be alternatively formed byconstructing the cover wall by a plurality of tongue pieces arrangedseparately from one another so as to confront the gas discharge ports ofthe inflator. With this construction, the mist from the individual gasdischarge ports adheres to the tongue piece covering the respective gasdischarge port. The mist from other gas discharge ports than theconfronting port hardly adheres to the respective tongue piece.Accordingly, the forming of mist agglomerates is prevented. Moreover,the tongue pieces are provided with spaces in between the neighboringtongue pieces, and great deal of the inflation gas from the gasdischarge ports flows toward the spaces. Therefore, the mist adhered tothe individual tongue pieces is likely to be blown off toward the spacesbetween the tongue pieces before growing to form mist agglomerates.

In this case, the smallest clearance between the gas discharge port andthe cover wall is desirably set within the range of 8 to 20 mm. If theclearance is under 8 mm, the cover wall is prone to be deformed, therebymaking difficult for the mist to adhere thereon. Even if the cover wallis not deformed, the pressure loss of the gas is increased, so that ittakes more time to inflate the airbag completely. If the clearance isover 20 mm, it is too far for the mist to adhere to the cover wall, sothat the meaning of providing the cover wall is lost.

In the case the mist growth prevention means is constructed by thethrough portion, the through holes, or the tongue pieces, it is desiredthat the airbag is provided at the opening peripheral edge with aprotection cloth arranged in the inner side of the base clothconstituting the bag shape of the airbag for the protection of the basecloth. The protection cloth is arranged up to the area over the vicinityof the leading end of the cover wall of the retainer in the completelyinflated airbag. With this construction, even if the mist flows out ofthe cover wall through the aforementioned through portion, the throughholes, or the spaces between the tongue pieces toward the part of theairbag neighboring the opening peripheral edge, it adheres to theprotection cloth arranged in the inner side of the base cloth.Therefore, the mist is prevented from adhering to the base clothconstituting the bag shape, or the outer shape of the airbag.

The inflator includes a flange having a plurality of recesses andretaining pawls. The retainer includes a plurality of bolts. The airbagand the inflator are secured to the bottom wall of the case by insertingthe bolts of the retainer through the opening peripheral edge of theairbag, the bottom wall of the case, and the recesses of the inflatorand fastening them into nuts, and by inserting the retaining pawls ofthe inflator through the bottom wall of the case to retain the openingperipheral edge of the airbag. With this construction, the number of thebolts used is reduced compared with the case of attaching the airbag andthe inflator to the bottom wall of the case only by the bolts of theretainer, which makes the detachment of the inflator easier inscrapping.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of the dashboard on which an airbag devicefor front passenger's seat of the first embodiment according to thepresent invention is mounted.

FIG. 2 is a schematic section of the first embodiment in deploymentalong the vehicle's longitudinal direction.

FIG. 3 is a schematic enlarged section of the airbag device of the firstembodiment along the vehicle's longitudinal direction.

FIG. 4 is a schematic enlarged section of the airbag device of the firstembodiment along the vehicle's transverse direction.

FIG. 5 shows the perspective views of a retainer, a case and an inflatoremployed in the airbag device of the first embodiment.

FIG. 6 is a perspective view of the airbag employed in the firstembodiment in solitarily inflated state.

FIG. 7 is a sectional view of the airbag employed in the firstembodiment in solitarily inflated state along the vehicle's longitudinaldirection.

FIG. 8 shows the plane views of the components of the airbag employed inthe first embodiment.

FIG. 9 illustrates the manufacturing process of the airbag employed inthe first embodiment.

FIG. 10 is a perspective view showing the folds of the airbag employedin the first embodiment in the preliminary folding.

FIG. 11 shows a preliminarily folded airbag of the first embodiment, asviewed from the gas inlet port side.

FIG. 12 shows a preliminarily folded airbag of the first embodiment, asviewed from the passenger's side wall side.

FIG. 13 is an end view taken along the line XIII—XIII of FIG. 11.

FIG. 14 is an end view taken along the line XIV—XIV of FIG. 11.

FIG. 15 is an end view taken along the line XV—XV of FIG. 11.

FIG. 16 is an end view taken along the line XVI—XVI of FIG. 11.

FIG. 17 shows the folding process after the preliminary folding of theairbag employed in the first embodiment.

FIG. 18 shows the folding process of the airbag employed in the firstembodiment, and shows the step after FIG. 17.

FIG. 19 illustrates the deployment of the first embodiment as viewedfrom the vehicle's side.

FIG. 20 is a graph showing the mass flow curve of the inflator employedin the first embodiment.

FIG. 21 is a graph showing the result of the frontal collision FRB testaccording to FMVSS No. 208-66FR65403 effective on May 28, 2003,conducted at 20 to 25 MPH speed to obtain the head deceleration data ofthe unbelted passenger dummy, for the airbag device of the firstembodiment, a conventional type, and a comparison example.

FIG. 22 shows a preliminarily folded airbag of a modification of thefirst embodiment, as viewed from the gas inlet port side.

FIG. 23 shows the preliminarily folded airbag in FIG. 22, as viewed fromthe passenger's side wall side.

FIG. 24 is an end view taken along the line XXIV—XXIV in FIG. 22.

FIG. 25 is a perspective view showing the folds of the airbag in FIG. 22in the preliminary folding.

FIG. 26 shows the folding process after the preliminary folding of theairbag in FIG. 22.

FIG. 27 is a sectional view of the airbag folded in FIG. 26 in themounted state on the vehicle.

FIG. 28 is a perspective view of the dashboard on which an airbag devicefor front passenger's seat of the second embodiment is mounted.

FIG. 29 is a schematic section along the vehicle's longitudinaldirection of the second embodiment in deployment.

FIG. 30 is a schematic enlarged section along the vehicle's longitudinaldirection of the airbag device of the second embodiment.

FIG. 31 is a schematic enlarged section along the vehicle's transversedirection of the airbag device of the second embodiment.

FIG. 32 shows the perspective views of an inflator, a retainer and acase employed in the airbag device of the second embodiment.

FIG. 33 shows the bottom views of the case and the inflator of theairbag device of the second embodiment being assembled.

FIG. 34 shows the bottom views illustrating the assembling of the airbagdevice of the second embodiment.

FIG. 35 is a bottom view of the airbag device of the second embodimentjust assembled.

FIG. 36 is a partial section taken along the line XXXVI—XXXVI of FIG.35, showing the airbag device of the second embodiment just assembled.

FIG. 37 is a partial section taken along the line XXVII—XXVII of FIG.35, showing the airbag device of the second embodiment just assembled.

FIG. 38 is a perspective view of the airbag employed in the secondembodiment in solitarily inflated state.

FIG. 39 is a sectional view of the airbag employed in the secondembodiment in solitarily inflated state along the vehicle's longitudinaldirection.

FIG. 40 shows the plane views of the components of the airbag employedin the second embodiment.

FIG. 41 illustrates the manufacturing process of the airbag employed inthe second embodiment.

FIG. 42 is an enlarged partial plane view showing the vicinity of theretainer of the second embodiment in use.

FIG. 43 is a perspective view of a modification of the retainer of thesecond embodiment.

FIG. 44 is an enlarged partial plane view of the retainer in FIG. 43 inuse.

FIG. 45 is a perspective view of yet another modification of theretainer.

FIG. 46 is an enlarged partial plane view of the retainer in FIG. 45 inuse.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be described below by way of embodiments shown in thedrawings. In addition, the invention is not limited to the embodiments.All modifications within the requirements of the claims and equivalentswith respect to the requirements should be included in the scope of theclaims.

FIGS. 1 and 2 illustrate a first embodiment of the airbag device M1 forfront passenger's seat of a top-mount type, which is arranged inside ofthe top surface 1 a of a dashboard (or an instrument panel) 1. Thisairbag device M1 includes an airbag 40 folded, an inflator 11 forsupplying the airbag 40 with inflation gas, a case 24 for housing andholding the airbag 40 and the inflator 11, a retainer 17 for attachingthe airbag 40 to the case 24, and an airbag cover 32 for covering thefolded airbag 40.

As shown in FIGS. 1 to 4, the airbag cover 32 is integral with thedashboard 1, in the first embodiment. The dashboard 1 includes a base 2on the back surface side and a coating layer 3 covering the outersurface of the base 2. The base 2 is made of hard synthetic resin suchas polypropylene, and the coating layer 3 has a foamed layer of foamablepolyurethane or the like, and a skin layer. At the portion of the airbagcover 32, there is arranged a soft portion 4 made of soft syntheticresin such as thermo-plastic elastomer of polyolefine or the like,instead of the base 2. The airbag cover 32 includes two doors 33F and33B respectively provided with a weakened breakable portion 35therearound. As shown in FIG. 1, the breakable portion 35 is arranged inan H-shape as viewed from above the dashboard 1. The two doors 33F and33B open toward the front and rear sides, respectively, around theirupper or lower ends as the hinges 34.

The airbag cover 32 further includes a joint wall portion 36 projecteddownward from the back surface to encircle the arrangement position ofthe doors 33F and 33B, and having a generally square cylindrical shape.The joint wall portion 36 includes the walls 36 a and 36 b confrontingeach other in the front and rear direction, and the walls 36 a and 36 bare provided with a plurality of retaining holes 37 at predeterminedpositions thereof. Retaining pawls 30 of the case 24 are inserted intothese retaining holes 37 so as to retain the joint wall portion 36. Thisretention of the joint wall portion 36 by the retaining pawls 30 securesthe connection of the joint wall portion 36 and the case 24, and helpthe airbag 40 inflated to push up the doors 33F and 33B and break thebreakable portion 35.

Here in the first embodiment, the soft portion 4 is arranged on the backside of the doors 33F and 33B of the airbag cover 32, and on the backside of the dashboard 1 in the vicinity of the hinges 34 of the doors33F and 33B, at both front and rear sides of the joint wall portion 36.Moreover, the joint wall portion 36 itself is formed of the soft portion4.

As shown in FIGS. 2 to 5, the case 24 is made of a sheet metal into agenerally rectangular parallel piped shape, and has a rectangularopening 24 a at the upper side. The case 24 includes a bottom wall 25 ofa rectangular plate shape, and a side wall 29 extended upward toward theairbag cover 32 from the outer circumferential edge of the bottom wall25 to have a generally square cylindrical shape. The bottom wall 25 hasa rectangular plate shape elongated in the left and right direction, andhas in its center a generally round insert hole 26 for inserting theupper portion 12 a of the inflator 11 from the lower side toward theairbag cover 32. In the periphery of the insert hole 26 of the bottomwall 25, there are formed mounting holes 27 for inserting through thebolts 20 of the retainer 17. The bottom wall 25 is further provided onthe lower surface thereof and at the left and right sides with brackets28 for securing the case 24 to the vehicular body 6. Each of thebrackets 28 is provided with a nut 28 a for fastening a bolt 9. On theside of the body 6, brackets 8 are extended from the reinforcement 7,and the bolt 9 is inserted through the mounting seat 8 a of the bracket8 and fastened into the nut 28 a. By fastening the bolts 9 into the nuts28 a, the case 24, or the airbag device M1 is secured to the body 6.

In the periphery of the insert hole 26 of the bottom wall 25, there isformed a rib 25 a protruded upward and encircling the insert hole 26.When the later-described base 18 of the retainer 17 is pressed on thebottom wall 25, the rib 25 a abuts against the lower surface of the base18, and helps improve the sealing property of the bottom wall 25 and theairbag 40 in the periphery 51 of the gas inlet port 50 (refer to FIG.4).

The side wall 29 of the case 24 is provided at the vehicle's front andrear upper ends thereof with a plurality of retaining pawls 30 turnedoutward and downward. As described above, the retaining pawls 30 areinserted into the retaining holes 37 of the joint wall portion 36 of theairbag cover 32 so as to retain the joint wall portion 36.

The inflator 11 is a pyro-type inflator, which generates inflation gasby burning reaction of a predetermined gas generating material, forexample, a gas generating material composition containing by weight ofthe material 34% nitroguanidine, 50% nitrate strontium, 9% sodium saltof carboxymethylcellulose, and 7% acid clay. As shown in FIGS. 2 to 6,the inflator 11 is a disc-type including a body 12 of a generallycylindrical shape. Moreover, the inflator 11 is a long mass flow typedrawing a mass flow curve as shown in FIG. 20. In the inflator 11 in thefirst embodiment, although the mass flow rate of the inflation gas issmall right after the ignition, it increases from 30 msec after ignitionon, compared with a conventional inflator, as shown in FIG. 20.Therefore, the airbag 40 inflated by the inflation gas from the inflator11 is able to protect a passenger in the front passenger's seatproperly.

The inflator 11 includes a body 12 and a flange 14 for attaching theinflator 11 to the case 24. The body 12 is charged with such apredetermined amount of gas generating material as to generate 2.4 molof combustion gas. The flange 14 is projected from the outercircumference of the body 12 in a generally square annular shape (or ina generally square plate shape), and is provided at its four cornerswith mounting holes 15 punched out. The individual mounting holes 15 areplaced in the positions corresponding to the individual mounting holes27 of the bottom wall 25 of the case 24. Each of the mounting holes 15has the same internal diameter as that of the mounting hole 27.

The body 12 has a cylindrical shape whose outer diameter is slightlysmaller than the internal diameter of the insert hole 26 of the bottomwall 25. The body 12 is provided on the outer circumferential side 12 bof the upper body 12 a above the flange 14 with a plurality of gasdischarge ports 13 for discharging the inflation gas G. In the firstembodiment, the gas discharge ports 13 are arranged in a zigzag mannerin the outer circumferential side 12 b of the upper body 12 a closer tothe top surface 12 c.

As shown in FIGS. 2 to 5, the retainer 17 is formed of a sheet metal,and includes a base 18 and a cover wall 21. The base 18 has an inserthole 19 opened generally in the same shape as the insert hole 26 of thecase 24. The cover wall 21 extends up toward the airbag cover 32 fromthe outer peripheral edge of the base 18 in a generally squarecylindrical shape.

The base 18 has a generally square outline, and is provided at its fourcorners 18 b with bolts 20 extended downward. When the retainer 17 isarranged within the airbag 40, the individual bolts 20 are inserted intothe mounting holes 52 of the airbag, 40, the mounting holes 27 of thebottom wall 25 of the case 24, and the mounting holes 15 of the flange14 of the inflator 11, and are fastened into the nuts 16. Thus theairbag 40 and the inflator 11 are attached to the bottom wall 25 of thecase 24. In other words, when the bolts 20 are fastened into the nuts16, the peripheral edge 51 of the gas inlet port 50 of the airbag 40 ispressed onto the bottom wall 25 by the base 18, thereby attaching theairbag 40 to the bottom wall 25, while the flange 14 of the inflator 11is pressed onto the periphery of the insert hole 26, thereby attachingthe inflator 11 to the bottom wall 25.

The cover wall 21 of the retainer 17 is constructed to cover the gasdischarge ports 13 of the inflator 11. The leading end 21 a of the coverwall 21 is extended upward up to the same level as the top surface 12 cof the inflator 11. The leading end 21 a is arranged only at thestraight portion 18 a of the outer edge of the base 18. Morespecifically, at the corners 18 b of the outer peripheral edge of thebase 18 where the bolts 20 are arranged, there are arranged recesses 22to separate the upper end 21 a of the cover wall 21.

These recesses 22 are arranged to regulate the amount of the inflationgas G flowing toward the airbag cover 32. In other words, the recesses22 are arranged to send a small amount of the inflation gas G out of thecover wall 21 therethrough to regulate the amount of the inflation gas Gflowing toward the airbag cover 32, and to constitute thelater-described mist growth prevention means B1 as well.

Here, the retainer 17 is formed by punching the insert hole 19, mountingholes for the bolts 20, and the recesses 22 in a sheet metal, by drawingit to form the base 18 and the cover wall 21, and by assembling thebolts 20.

As shown in FIGS. 6 and 7, the airbag 40 has, as its shape completelyexpanded and inflated, a passenger's side wall 41 to be arrangedgenerally in the vertical direction and closer to the passenger, and aside wall portion 48 extended toward the vehicle's front side from theouter peripheral edge of the passenger's sidewall 41 while narrowinglike a generally conical shape. A gas inlet port 50 opened in a roundshape is arranged to introduce the inflation gas G into the airbag 40(refer to FIG. 7) in the front side of the lower side wall 49 of theside wall portion 48 to be positioned at the lower side when completelyexpanded and inflated.

In the first embodiment, the capacity of the airbag 40 is 110 l whencompletely inflated.

Internally, the airbag 40 is provided with a commutator cloth 69covering the gas inlet port 50 for redirecting the flow of theflowing-in inflation gas G. As shown in FIG. 2, the vicinity of thetransverse center 69 a of the commutator cloth 69 and a part of frontand rear openings 69 b and 69 c of the commutator cloth 69 are disposedabove the top surface 1 a of the dashboard 1 when the airbag 40 isinflated.

In the periphery 51 of the gas inlet port 50, there are formed fourmounting holes 52. The bolts 20 of the retainer 17 are inserted into themounting holes 52, so that the airbag 40 is fixed to the bottom wall 25of the case 24. In the left and right sides of the side wall portion 48,a vent hole 64 is provided to emit extra inflation gas, respectively.The airbag 40 is further provided internally near the mounting holes 52in the periphery of the gas inlet port 50 with a reinforcing cloth 67having a generally square annular shape.

When the airbag device M1 is mounted on the vehicle by fixing the airbag40 to the case bottom wall 25 by the retainer 17, and by securing thecase 24 to the body 6, the front edge 51 a of the opening peripheraledge 51 is positioned slightly higher than the rear edge 51 b, so thatthe opening face of the gas inlet port 50 is arranged generallyhorizontally together with the opening peripheral edge 51 (refer to FIG.19).

As shown in FIGS. 8 and 9, the airbag 40 is formed by sewing up two basecloths, i.e., the first base cloth 65 and the second base cloth 66. Thefirst base cloth 65 is shaped to be a combination of two generallyhexagonal portions, i.e., the upper portion 65 a and the lower portion65 e, and resultingly has a gourd-shape having the left and right edgeat the longitudinal center recessed. The second base cloth 66 has agenerally round shape approximate to a generally hexagonal shape. Theseplanar base cloths 65 and 66 are constructed to provide the solid airbag40 by sewing work.

The second base cloth 66 constitutes the generally entire area of thepassenger's side wall 41 of the airbag 40, whereas the first base cloth65 constitutes the generally entire area of the side wall portion 48 ofthe airbag 40. Moreover, the upper portion 65 a of the first base cloth65 constitutes the generally entire area of the upper side wall 59 ofthe side wall portion 48, whereas the lower portion 65 e of the firstbase cloth 65 constitutes the generally entire area of the lower sidewall 49 of the side wall portion 48.

The first and second base cloths 65 and 66, the reinforcing cloth 67 andthe commutator cloth 69 are formed of a woven fabric of polyester,polyamide yarn or the like without silicon coating or the like.

In the first embodiment, the first and second base cloths 65 and 66 areplain weaved with 420 denier long and multifilament yarn of polyamide,at the weave density of 56 warp yarn×55 weft yarn per square inch. Thegas permeability rate of the first and second base cloths 65 and 66 is0.69 l/cm²/min which is under 1.0 l/cm²/min at 20 kPa air pressure, andits weight is 220 g/m² which is under 230 g/m².

As shown in FIGS. 6 and 7, the commutator cloth 69 is larger than thelongitudinal and transverse dimensions of the gas inlet port 50 so as tocover the gas inlet port 50 within the airbag 40. Its longitudinalsection upon the expansion of the airbag 40 is arcuate bulging upwardaway from the gas inlet port 50.

In the first embodiment, as shown in FIGS. 8 and 9, the commutator cloth69 is prepared as a commutator cloth material 68 before the attachmentto the airbag 40. The commutator cloth material 68 has an opening 68 acorresponding to the gas inlet port 50 and band portions 68 b and 68 bextending from the vehicle's left and right sides of the opening 68 a.The commutator cloth 69 is formed by sewing up the leading ends of theband portions 68 b and 68 b. The commutator cloth material 68 furtherincludes mounting holes corresponding to the mounting holes 52.

To manufacture the airbag 40, as shown in FIGS. 8 and 9A, thereinforcing cloth 67 and the commutator cloth material 68 are firstlystitched to the to-be inner side of the first base cloth 65 at theopening peripheral edge 51 of the gas inlet port 50 by the stitchingyarn S. As shown in FIG. 9B, subsequently, the leading ends of the bandportions 68 b of the commutator cloth material 68 are stitched uptogether in an arcuate manner by the stitching yarn S, thereby to formthe commutator cloth 69.

In the first embodiment, the first base cloth 65 has been provided withthe vent holes 64, the gas inlet port 50 and the mounting holes 52 inadvance, while the commutator cloth material 68 and the reinforcingcloth 67 have been provided with the gas inlet port 50 (or 68 a) and themounting holes 52 in advance. However, the vent holes 64, the gas inletport 50 and the mounting holes 52 may be made after the reinforcingcloth 67 and the commutator cloth material 68 are stitched to the firstbase cloth 65.

As shown in FIGS. 9B and 9C, thereafter, the first base cloth 65 isfolded back on the first base line X1 extending in the transversedirection between the upper portion 65 a and the lower portion 65 e.Then the straight edges 65 b and 65 f of the upper and lower portions 65a and 65 b, respectively, near the first base line X1 are stitched uptogether, and the other straight edges 65 c and 65 g are stitched uptogether, too.

Subsequently as shown in FIGS. 9C and 9D, the upper portion 65 a isfolded back on the second base line X2 extending between the portionsprojected in the transverse directions, so that the unstitchedperipheral edges 65 d and 65 h of the upper and lower portions 65 a and65 e are separated and developed flatly. The outer shape in thisexpanded state is the same as the outer shape of the second base cloth66.

Then as shown in FIGS. 9D and 9E, the second base cloth 66 is appliedhereon, and the individual outer peripheral edges are stitched up by thestitching yarn S. Thus the airbag 40 is formed into a bag shape so thatthe stitch margin may not appear on the outer surface.

Thereafter, the airbag 40 is reversed inside out utilizing the gas inletport 50.

If it is difficult to reverse the airbag 40 from the gas inlet port 50because of the presence of the commutator cloth 69, the ends of the bandportions 68 b of the commutator cloth material 68 may be stitched afterthe reverse of the airbag 40 by pulling out the band portions 68 b fromthe gas inlet port 50.

The mounting of the airbag 40 thus manufactured on the vehicle isstarted by placing the retainer 17 inside of the airbag 40 so that thebolts 20 may be protruded from the mounting holes 52, and then foldingthe airbag 40. Then the folded airbag 40 is wrapped by a breakablewrapping sheet 39 (refer to FIG. 3) to keep the folded-up state.

The airbag 40 is folded through the preliminary folding step, and thenthrough the transverse folding step and the vertical folding step.

In the preliminary folding step, a preliminarily folded airbag 70 isformed, as shown in FIGS. 11 and 12. In the preliminary folding, theportion 46 near the upper edge 42 of the passenger's side wall 41 isplaced over the gas inlet port 50 to confront the gas inlet port 50 inthe vertical direction (refer to FIG. 16), and the remainder of thepassenger's side wall 41 is overlaid on the lower side wall 49 of theside wall portion 48 flatly. Further in the first embodiment, the sidewall portion 48 is so preliminarily folded that the generally entirearea of the passenger's side wall 41 may remain flat except thevicinities of the left edge 44 and the right edge 45.

FIGS. 10 to 16 illustrate the preliminary folding of the side wallportion 48 of the first embodiment. The portions 53 and 54 on the leftand right sides of the gas inlet port 50 on the side wall portion 48,and the portion 60 near the joint portion with the passenger's side wallupper edge 42 are folded on valley folds CL, CR and CH, respectively.More specifically, the left portion 53 and the right portion 54 of thegas inlet port 50 are folded so that the generally intermediate portions53 a and 54 a to the left and right edges 44 and 45 of the passenger'sside wall 41 flatly developed may be brought closer to the gas inletport 50, i.e., the folds CL and CR may be brought closer to each other,and may be arranged closer to the passenger's side wall 41 with respectto the gas inlet port 50. Then the left and right portions 53 and 54 arefolded in on the valley folds CL and CR extending along the longitudinaldirection. On the other hand, the portion 60 in the side wall portion 48near the upper edge 42 is folded so that the generally intermediateportion 59 a between the projected top 61 or the front end of the valleyfolds CL and CR in the upper side wall 59 and the passenger's side wallupper edge 42 may be brought closer to the gas inlet port 50 and placedcloser to the passenger's side wall 41 with respect to the gas inletport 50. Then the portion 60 near the upper edge is folded in on thevalley fold CH extending along the transverse direction. As shown inFIGS. 15 and 16, this fold CH is arranged in the front side of the rearedge 51 b of the gas inlet port 50.

The preliminary folding can be made by gripping the generallyintermediate portion between the transverse center of the front edgeside 51 a of the gas inlet port 50 in the side wall portion 48 and thetransverse center of the passenger's side wall upper edge 42, i.e., theportion to be the projected top 61, and the transverse center 56 a ofthe rear side portion 56 of the gas inlet port 50 in the side wallportion 48, and by pulling the grip portions 61 and 56 a in the frontand rear directions to separate them from each other. With respect tothe grip portion 56 a in the rear side portion 56, it is desired to gripthe portion as near the passenger's side wall lower edge 43 as possible,so that the generally entire area of the passenger's side wall 41 mayremain flat in the preliminary folding.

Here in the first embodiment, the portion 62 in the middle of the frontside portion 55 of the gas inlet port 50 and the projected top 61 in theside wall portion 48 is valley-folded toward the gas inlet port 50 sothat the opening peripheral edge 51 of the gas inlet port 50 may be flatand parallel to the passenger's side wall 41.

In the preliminarily folded airbag 70 of the first embodiment, thevalley folds CH and 62 in the upper side wall 59 positioned at the upperside of the gas inlet port 50 in the side wall portion 48 are arrangedat the front side of the rear edge 51 b of the gas inlet port 50, asshown in FIGS. 15 and 16. More specifically, in the preliminarily foldedairbag 70, the upper side wall 59 is folded and disposed in the frontrange of the rear edge 51 b of the gas inlet port 50.

After the preliminary folding, the transverse folding is applied to therear side portion 71 and the front side portion 72 of the gas inlet port50 in the preliminarily folded airbag 70. As shown in FIGS. 11, 17A,17B, 18A and 18B, the rear side portion 71 and the front side portion 72are folded on the folds extending in the transverse direction so thatthe ends 71 a and 72 a are brought closer to the gas inlet port 50. Inthe first embodiment, the rear side portion 71 is roll-folded from therear end 71 a on the lower side wall 49, and then folded back on thepassenger's side wall 41. The front side portion 72 is folded in abellows fashion.

After the transverse folding, the vertical folding is applied to theleft side portion 73 and the right side portion 74 of the gas inlet port50 of the airbag 40 transversely folded. As shown in FIGS. 18B and 18C,the left side portion 73 and the right side portion 74 are folded on thefolds extending in the longitudinal direction so that the ends 73 a and74 a are brought closer to the gas inlet port 50. In the firstembodiment, the left and right side portions 73 and 74 are roll-foldedto bring the ends 73 a and 74 a toward the lower side wall 49.

When the airbag 40 is completely folded through the vertical folding,the folded airbag 40 is wrapped by a breakable wrapping sheet 39 to keepthe folded-up state, as described hereinbefore.

Then, the folded airbag 40 is located on the bottom wall 25 of the case24 from the opening 24 a by inserting the individual bolts 20 into themounting holes 27 from above. Subsequently, the upper portion 12 a ofthe body 12 of the inflator 11 is inserted into the insert hole 26, thegas inlet port 50, and the insert hole 19 from the lower side, and theindividual bolts 20 protruded downward from the bottom wall 25 areinserted through the mounting holes 15 of the flange 14 of the inflator11. Thereafter, the nuts 16 are fastened into the bolts 20 protrudedfrom the flange 14 of the inflator 11. Thus the folded airbag 40 and theinflator 11 are attached to the bottom wall 25 of the case 24.

Thereafter, the side wall 20 of the case 24 is inserted within the jointwall portion 36 of the airbag cover 32 in the dashboard 1 mounted on thevehicle, and the individual retaining pawls 30 of the case 24 areinserted into the retaining holes 37 on the joint wall portion 36. Thusthe retaining pawls 30 are retained by the joint wall portion 36. If thebolts 9 are fastened into the nuts 28 a of the individual brackets 28through the mounting seats 8 a, the airbag device M1 for frontpassenger's seat is mounted on the vehicle.

Alternatively, the mounting of the airbag device M1 on the vehicle maybe made by assembling the case 24 with the airbag 40 and the inflator 11to the airbag cover 32 of the dashboard 1, and securing this airbagdevice M1 to the body 6 with the bolts 9 when attaching the dashboard 1to the vehicle.

After mounting the airbag device M1 on the vehicle, when the inflationgas G is discharged from the individual gas discharge ports 13 of theinflator 11, the airbag 40 inflates and breaks the wrapping sheet 39.The airbag 40 further breaks the breakable portion 35 and opens thedoors 33F and 33B of the airbag cover 32 as indicated by thedouble-dotted lines in FIGS. 2 and 3, and then protrudes from theopening 38 made by the opening of the doors 33F and 33B.

The airbag 40 thus completes the inflation, and emits the extra gas fromthe vent holes 64. Here, the reference numeral W in FIG. 2 designatesthe windshield.

Since the airbag device M1 of the first embodiment employs the inflator11 of pyro- and long mass flow type, the inflator 11 is compact, and isable to expand and inflate the airbag 40 for front passenger's seatproperly.

In the airbag device M1 for front passenger's seat of the firstembodiment, the gas permeability rate of the base cloths 65 and 66constituting the airbag 40 is 0.69 l/cm²/min which is less than 1.0l/cm²/min at 20 kPa air pressure. Therefore, the gas leakage isprevented when the inflation gas G is introduced into the airbag 40 fromthe inflator 11, so that the characteristic property of the long massflow type inflator 11 is most made use of. As a result, the airbagdevice M1 is able to provide the smooth inflation state of the airbag40.

If the gas permeability rate of the base cloths 65 and 66 is over 1.0l/cm²/min at 20 kPa air pressure, the inflation gas G becomes morelikely to leak, thereby to lower the reaction force of the airbag 40occurring from 30 msec after ignition of the inflator 11 on. Then themeaning of employing the long mass flow type inflator 11 is lost.

In the first embodiment, moreover, since the weight of the airbag 40 is220 g/m², which is less than 230 g/m², it contributes to the weightreduction of the airbag 40.

Moreover, the long mass flow type inflator 11 itself is able tocontribute to the weight reduction by reducing the discharge amount ofthe inflation gas G, since the gas permeability rate of the airbag 40 islow. Here, if the weight of the airbag 40 is over 230 g/m², it cancelsthe merit of weight reduction.

In the airbag device M1 for front passenger's seat of the firstembodiment, therefore, it is able to secure the smooth expansion andinflation of the airbag 40, and to contribute to the weight reductioneven if employing an inflator 11 of long mass flow type.

In the first embodiment, especially, the amount of the inflation gas Gdischarged from the inflator 11 is 2.4 mol, less than 2.8 mol, againstthe 110 l capacity of the airbag 40 completely inflated. Here, when theamount of the gas discharged is 2.4 mol, the gas discharge rate per unitvolume of the airbag is 0.022 mol/l, and when the amount discharged is2.8 mol, the gas discharge rate per unit volume is 0.026 mol/l.Accordingly, the inflator 11 is able to make lighter than a conventionalpyro-type inflator discharging 3.2 to 3.5 mol gas against the 110 lcapacity of the airbag, whose discharge rate per unit volume of theairbag is 0.029 to 0.032 mol/l. Thus the inflator 11 contributes to theweight reduction of the airbag device M1. Of course, the smoothexpansion and inflation of the airbag 40 is not hindered even with acompact inflator 11, since the gas leakage from the airbag 40 does notoccur.

The inflator 11 of the first embodiment enables 25% weight reductioncompared with a conventional pyro-type inflator for an airbag of 110 lcapacity.

Further in the first embodiment, the airbag 40 is internally providedwith the commutator cloth 69 which receives the inflation gas G flowingoutward from the inside of the dashboard 1 and changes its flow towardthe vehicle's front and rear directions at a position out of thedashboard 1 and within the airbag 40 when the airbag 40 inflates withthe inflation gas G.

As indicated by the double-dotted lines in FIG. 2, and as shown in FIG.7, in this construction, the inflation gas G flowing into the airbag 40is guided by the commutator cloth 69 toward the directions GF and GBperpendicular to the direction FL at the position out of the dashboard1, and the inflation gas G is prevented from abutting directly againstthe inner surface of the airbag 40. In other words, the inflation gas Gdoes not straightly abut the inner surface of the airbag 40 composed ofthe base cloths 65 and 66 in the direction FL in which the inflation gasG initially flows into the airbag 40. Therefore, the damage to the basecloths 65 and 66 constituting the airbag 40 is reduced, and the gasleakage from the airbag 40 is prevented. As a result, the gaspermeability of the airbag 40 mounted on the vehicle is further lowered,thereby promoting the expansion and inflation of the airbag 40.

In the airbag 40 of the first embodiment, moreover, the reinforcingcloth 67 is arranged along the vehicle's front and rear directions so asto confront the openings 69 b and 69 c of the commutator cloth 69helping the gas G to flow toward the front and rear sides when theairbag 40 is inflated, as shown in FIG. 7. Thus the inflation gas GF andGB guided by the commutator cloth 69 toward the front and reardirections hardly contact the first base cloth 65 directly, so that thedamage to the first base cloth 65 by the inflation, gas GF and GB isreduced.

FIG 21 shows the result of the frontal collision FRB (Full Rap Barrier)test according to FMVSS No. 208-66FR65403 effective on May 28, 2003 forevaluating the restraint performance of the airbag 40 of the airbagdevice M1 of the first embodiment. The test was conducted at 20 to 25MPH speed to obtain the head deceleration data of the unbelted passengerdummy. The solid line in FIG. 21 shows a plot of the first embodiment.The double-dotted line shows a plot of a comparison example whose gaspermeability rate is 1.39 l/cm²/min at 20 kPa air pressure. Otherconditions such as the folding manner and the inflator of the comparisonexample are the same as that of the first embodiment. The broken lineshows a plot of an airbag device employing a conventional inflator whosedischarge amount is 3.5 mol, with other conditions the same as the firstembodiment.

FIG. 21 shows that the head deceleration in the airbag 40 of the firstembodiment is over 120 m/s², which surpasses 100 m/s², in the decisionarea (55 to 75 msec). Therefore, the airbag 40 has an enough reactionforce to protect a passenger, and is suitable with respect to therestraint performance of a passenger in the front passenger's seat. Onthe other hand, when employing a conventional inflator, the decelerationsometimes falls below 100 m/s², which is lower than the first embodimentin respect of the reaction force to restrain a passenger. Further in thecase of the comparison example employing an airbag with high gaspermeability, the deceleration is even lower compared with the caseemploying a conventional inflator.

In the airbag device M1 of the first embodiment, moreover, the airbag 40expands and inflates upon admitting the inflation gas G from the gasinlet port 50 while unfolding the transverse folds and vertical folds.

At this time, in the airbag 40 of the first embodiment, the portion 46near the upper edge 42 in the passenger's side wall 41 is disposed overthe gas inlet port 50 to confront the gas inlet port 50 in thepreliminary folding. This portion 46 near the upper edge of thepassenger's side wall 41 is pushed intensely upward by the pressure F(refer to FIGS. 14 to 16) of the inflation gas G initially dischargedprior to other portions of the passenger's side wall 41 such as thelower edge 43 side. As shown in FIG. 19, therefore, the passenger's sidewall 41 thereafter is easily disposed generally along the verticaldirection. Here in the first embodiment, the pressure F of the inflationgas G is applied to the portion 46 near the upper edge of thepassenger's side wall 41 while the commutator cloth 69, thevalley-folded portion 62 of the side wall portion 48, the portion 60near the upper edge of the side wall portion 48 (the intermediateportion 59 a), and the transverse centers 53 a and 54 a of the side wallportion 48 being interposed.

Since the portion 46 near the upper edge of the passenger's side wall 41is pushed up intensely, the transverse and vertical folds are quicklyunfolded, thereby helping expand the passenger's side wall 41 widely.

In the airbag device M1 for front passenger's seat of the firstembodiment, therefore, the passenger's side wall 41 disposed generallyperpendicularly to the gas inlet port peripheral edge 51 is quicklydeployed generally along the vertical direction when the airbag 40expands and inflates, and the airbag 40 is widely expanded so as not toapply a partial pressure to the passenger.

Moreover in the first embodiment, the generally entire area of thepassenger's side wall 41 is left flatly expanded when folding the sidewall portion 48 in the preliminary folding. The passenger's side wall 41is not folded up. Therefore, the preliminary folding is easilyconducted. Moreover, since the passenger's side wall 41 is flatlyexpanded, it is able to move toward the passenger in a state widelyexpanded transversely and vertically when the airbag 40 expands andinflates, compared with the case of folding also the passenger's sidewall 41. Therefore, it is able to suppress the speed of the passenger'sside wall 41 moving toward the passenger.

In the first embodiment, furthermore, the upper side wall 59 positionedat the upper side of the gas inlet port 50 is folded in the range infront of the rear edge 51 b of the gas inlet port 50. It is not extendedto the rear side of the gas inlet port 50. Accordingly, when theinflation gas G is introduced from the gas inlet port 50, the portion 46near the upper edge of the passenger's side wall 41 is pushed up withthe upper side wall 59 interposed, and the upper side wall 59 itselfalso is pushed up. At this time, the upper side wall 59 is released fromthe gas inlet port 50 while being unfolded. As a result, the portion 46near the upper edge of the passenger's side wall 41 comes to confrontthe gas inlet port 50 directly, and helps the passenger's side wall tobe disposed generally vertically.

In the first embodiment, moreover, in the preliminary folding of theside wall portion 48 of the airbag 40, the left and right portions 53and 54 of the gas inlet port 50 are respectively folded on the valleyfolds CL and CR extended in the vehicle's longitudinal direction so thatthe generally intermediate portions 53 a and 54 a to the left and rightedges 44 and 45 of the passenger's side wall 41 flatly expanded may bebrought closer to the gas inlet port 50 behind the gas inlet portperipheral edge 51. The portion 60 near the upper edge 42 in the sidewall portion 48 is folded in on the valley fold CH extending in thevehicle's transverse direction. In other words, the side wall portion 48of the airbag 40 is folded symmetrically with respect to the gas inletport 50, and therefore, the preliminary folding is easily conducted.

Especially, the preliminary folding of the side wall portion 48 can bemade smoothly by gripping the generally intermediate portion 61 betweenthe transverse center of the front edge side 51 a of the gas inlet port50 in the side wall portion 48 and the transverse center of thepassenger's side wall upper edge 42, and the transverse center 56 a ofthe rear side of the gas inlet port 50 in the side wall portion 48, andby pulling the grip portions 61 and 56 a in the front and reardirections to separate them from each other. Therefore, the preliminaryfolding work is further facilitated.

Further in the first embodiment, the valley fold CH in the upper sidewall 59 is disposed in front of the rear edge 51 b of the gas inlet port50 so as to leave a blank space between the rear edge 51 b. Accordingly,the pressure F of the inflation gas G applies directly to the portion 46near the upper edge of the passenger's side wall 41 through the space.As a result, the passenger's side wall 41 is even more easily disposedgenerally in the vertical direction.

In the first embodiment, the valley-folded portion 62, i.e. the portionin the side wall portion 48 from the front portion 55 of the gas inletport 50 to the projected top 61, is disposed in the rear side of thefront edge 51 a of the gas inlet port 50 and confronts the gas inletport 50. However, the valley-folded portion 62 is disposed closely tothe gas inlet port 50, and therefore, does not affect the pressure F ofthe inflation gas G in pushing up the portion 46 near the upper edge ofthe passenger's side wall 41.

FIGS. 22 to 25 illustrate a modification of the first embodiment withrespect to the preliminary folding of the side wall portion 48. Theairbag 40A includes the first and second base cloths 65 and 66, thereinforcing cloth 67, and the commutator cloth material 68, and has thesame shape as the airbag 40. The preliminary folding is applied to thisairbag 40A to form the preliminarily folded airbag 70A.

In the preliminarily folded airbag 70A, the valley fold CH in the sidewall portion 48 is positioned at the rear side of the rear edge 51 b ofthe gas inlet port 50. The preliminary folding is applied with thepassenger's side wall 41 flatly expanded, by gripping and pulling thegenerally intermediate portion 61 between the transverse center of thefront edge side 51 a of the gas inlet port 50 in the side wall portion48 and the transverse center of the passenger's side wall upper edge 42,and the transverse center 43 a in the lower edge of the passenger's sidewall 41. The grip portion 43 a is the rear side portion of the gripportion 56 a in the aforementioned airbag 40. In other words, thepreliminary folding of the airbag 40A can be conducted by shifting thepassenger's side wall 41 rearward, gripping the portions 61 and 43 a,and pulling the grip portions 61 and 43 a in the front and reardirections to separate them from each other. At this time, the side ofthe grip portion 43 a is pulled more largely in the airbag 40A.

Although the valley fold CH in the side wall portion 48 is positioned atthe rear side of the rear edge 51 b of the gas inlet port 50 in thepreliminarily folded airbag 70A, the fold CH is disposed close to therear edge 51 b. In other words, in the preliminarily folded airbag 70A,the upper side wall 59 of the side wall portion 48 is arranged in therange from the vicinity of the rear edge 51 b of the gas inlet port 50toward the front side, as a result of the folding.

As shown in FIGS. 26A, 26B, 26C and 26D, the preliminarily folded airbag70A undergoes the transverse and vertical folding, as the preliminarilyfolded airbag 70. More specifically, the rear side portion 71 of the gasinlet port 50 in the preliminarily folded airbag 70A is roll-folded onthe folds extending in the transverse direction to bring the end 71 acloser to the gas inlet port 50, while the front side portion 72 of thegas inlet port 50 is folded back to bring the end 72 a closer to the gasinlet port 50. Thereafter, the left side portion 73 and the right sideportion 74 of the gas inlet port 50 are vertically folded on the foldsextending in the longitudinal direction to bring the individual ends 73a and 74 a closer to the gas inlet port 50. In the illustratedembodiment, the left and right side portions 73 and 74 are folded on thepassenger's side wall 41 in a bellows fashion after folding back theends 73 a and 74 a toward the lower side wall 49.

After the folding work, the airbag 40A is assembled into the airbagdevice M1 to be mounted on the vehicle, as the airbag 40 (refer to FIG.27).

Since the valley fold CH in the side wall portion 48 is positioned atthe rear side of the rear edge 51 b of the gas inlet port 50 in theairbag 40A, or in the preliminarily folded airbag 70A, the pressure F ofthe inflation gas G does not apply directly to the portion 46 near theupper edge, as in the aforementioned airbag 40. In the preliminarilyfolded airbag 70A, however, the upper side wall 59 in the side wallportion 48 is arranged in the range from the vicinity of the rear edge51 b of the gas inlet port 50 toward the front side. Accordingly, whenthe inflation gas G is introduced from the gas inlet port 50, theportion 46 near the upper edge of the passenger's side wall 41 is pushedup with the upper side wall 59 interposed, and then the upper side wall59 itself is also pushed up. Along with the rising, the upper side wall59 is unfolded, and is released from the gas inlet port 50. Even if thevalley fold CH in the side wall portion 48 is positioned at the rearside of the rear edge 51 b of the gas inlet port 50, therefore, theupper side wall 59 is unfolded to make the portion 46 near the upperedge of the passenger's side wall 41 confront the gas inlet port 50directly. As a result, the passenger's side wall 41 is easily arrangedgenerally in the vertical direction.

In the airbag 40A, moreover, since the side wall portion 48 is foldedwhile leaving the generally entire area of the passenger's side wall 41flatly expanded as in the airbag 40, the same working-effects as theairbag 40 are obtained.

Here in the airbag 40 of the first embodiment expanding and inflating,the portion 46 near the upper edge of the passenger's side wall 41 ispushed up by the inflation gas G from the gas inlet port 50, and thecommutator cloth 69 bulges upward in an arcuate shape. Then theinflation gas G abuts against the commutator cloth 69, and is dividedinto the gas GF flowing toward the vehicle's front side and the gas GBflowing rearward, as shown in FIG. 7. At this time, the sectional shapeof the commutator cloth 69 along the vehicle's longitudinal directionupon the inflow of the inflation gas G is a curve bulging away from thegas inlet port 50. Accordingly, the inflation gas GB flowing toward thevehicle's rear side derived from the inflation gas G flows toward thetop surface 1 a of the dashboard 1 along the curve of the commutatorcloth 69, not in parallel to the dashboard top surface 1 a. As a result,the folded portion 71 of the airbag 40 is expanded rearward along thetop surface 1 a of the dashboard 1, thereby to expand the passenger'sside wall 41 as wide as possible.

After the preliminary folding, in the first embodiment, the airbags 40and 40A go through the transverse folding first, and then the verticalfolding. However, the transverse folding may be conducted after thevertical folding, or alternatively, the vertical folding may beinterposed in the course of the transverse folding, and then thetransverse folding may be restarted to complete the folding work.Further alternatively, the transverse folding may be interposed in thecourse of the vertical folding, and then the vertical folding may berestarted to complete the folding work.

Further alternatively, with respect to the transverse folding after thepreliminary folding, the front side portion 72 may be roll-folded tobring the end 72 a toward the passenger's side wall 41, instead ofbellows-folding. The front side portion 72 may be placed on the rearside portion 71 after being folded, as shown in FIG. 26. Alternatively,the front side portion 72 may be placed in front of the rear sideportion 71 folded, disposing the end 72 a below the rear side portion 71folded.

With respect to the vertical folding after the preliminary folding,moreover, the left and right side portions 73 and 74 may bebellows-folded without rolling in the ends 73 a and 74 a or may benormally roll-folded.

As shown in FIGS. 3 and 4, in the airbag device M1 for front passenger'sseat of the first embodiment, the retainer 17 is provided with the coverwall 21 extended toward the airbag cover 32 from the base 18 for guidingthe inflation gas G up and toward the airbag cover 32 in the spacebetween itself and the end portion of the inflator 11 having the gasdischarge ports 13, or the outer circumferential side 12 b of the upperportion 12 a.

In the airbag device M1 of the first embodiment, therefore, when theinflation gas G is discharged from the gas discharge ports 13 of theinflator 11, it fills the space between the cover wall 21 of theretainer 17 and the outer circumferential side 12 b of the upper portion12 a of the inflator 11 with the gas discharge ports 13, as shown inFIGS. 3 and 4. Then the gas G flows up toward the airbag cover 32, sincethe cover wall 21 is extended toward the airbag cover 32. As a result,the airbag cover 32 subjected to the pressure of the inflation gas Gquickly breaks the breakable portion 35, and opens the doors 33F and 33Bsmoothly.

At this time, the part 63 of the airbag 40 (refer to FIGS. 3 and 4)neighboring the opening peripheral edge 51 held by the base 18 of theretainer 17 is blocked by the cover wall 21 of the retainer 17.Therefore, it is protected from the heated inflation gas G.

The cover wall 21 has recesses 22 at the corners 18 b of the base 18,and the part 63 of the airbag 40 is directly subjected to the inflationgas G from the recesses 22. However, only a small quantity of the gas Gflows to the part 63, and the part 63 is provided with the reinforcingcloth 67 and the commutator cloth 69. Therefore, the first base cloth 65does not sustain such damage as to lead to the gas leakage.

In the first embodiment, the cover wall 21 of the retainer 17 isarranged in a generally square cylindrical shape. However, the coverwall 21 may have a generally round cylindrical shape encircling the body12 of the inflator 11.

FIGS. 28 and 29 illustrate a second embodiment of the airbag device M2for front passenger's seat of a top-mount type, which is arranged insideof the top surface 1 a of a dashboard 1. This airbag device M2 includesan airbag 140 folded, an inflator 111 for supplying the airbag 140 withinflation gas, a case 124 for housing and holding the airbag 140 and theinflator 111, a retainer 117 for attaching the airbag 140 to the case124 and an airbag cover 132 for covering the folded airbag 140, as thefirst embodiment.

As shown in FIGS. 28 to 31, the airbag cover 132 is integral with thedashboard 1, as the first embodiment. The airbag cover 132 includes twodoors 133F and 133B respectively provided with a weakened breakableportion 135 therearound. As shown in FIG. 28, the breakable portion 135is arranged in an H-shape as viewed from above the dashboard 1. The twodoors 133F and 133B open toward the front and rear sides, respectively,around their upper or lower ends as the hinges 134.

The airbag cover further includes a joint wall portion 136 projecteddownward from the back surface to encircle the arrangement position ofthe doors 133F and 133B, and having a generally square cylindricalshape, as the first embodiment. The joint wall portion 136 includes thewalls 136 a and 136 b confronting each other in the front and reardirection, and the walls 136 a and 136 b are provided with a pluralityof retaining holes 137 at its predetermined positions. Retaining pawls130 of the case 124 are inserted into these retaining holes 137 so as toretain the joint wall portion 136.

As shown in FIGS. 29 to 32, the case 124 is made of a sheet metal into agenerally rectangular parallel piped shape, and has a rectangularopening at the upper side, as the case 24 in the first embodiment. Thecase 124 includes a bottom wall 125 of a rectangular plate shape, and aside wall1 129 extended upward toward the airbag cover 132 from theouter circumferential edge of the bottom wall 125 in a generally squarecylindrical shape. The bottom wall 125 has a rectangular plate shapeelongated in the left and right directions, and has in its center agenerally round insert hole 126 for inserting the upper portion 112 a ofthe inflator 111 from the lower side toward the airbag cover 132.

In the periphery of the insert hole 126 of the bottom wall 125, thereare formed mounting holes 127 for inserting through the two bolts 120 ofthe retainer 117, and insert holes 125 a for inserting through the tworetaining pawls 114 c of the inflator 111. The insert holes 125 a aredisposed in the positions corresponding to the later-described retainingholes 118 a of the retainer 117 and the mounting holes 150 of the airbag140, and are opened in the same shape as those. Each of the insert holes125 a is a combination of a large hole 125 b which the neck 114 e andthe head 114 f of the retaining pawl 114 c of the inflator 111 can gothrough, and a small hole 125 c communicating with the large hole 125 b.The neck 114 e of the retaining pawl 114 c can go through the small hole125 c, but the head 114 f of the retaining pawl 114 c cannot go throughthe small hole 125 c in the vertical direction.

The bottom wall 125 is further provided on its lower surface and at theleft and right sides with brackets 128 for securing the case 124 to thevehicular body 6, as the case 24 in the first embodiment. Each of thebrackets 128 is provided with a nut 128 a for fastening a bolt 9. Thebolt 9 is inserted through the mounting seat 8 a of the bracket 8 andfastened into the nut 128 a. By fastening the bolts 9 into the nuts 128a, the case 124, or the airbag device M2 is secured to the body 6.

Here, the two mounting holes 127 are disposed at the rear side in thecase 124 closer to a not-shown glove box as the case 124 is mounted onthe vehicle.

The side wall 129 of the case 124 is provided at the vehicle's front andrear upper ends with a plurality of retaining pawls 130 turned outwardand downward, as the case 24 in the first embodiment. As describedabove, the retaining pawls 130 are inserted into the retaining holes 137of the joint wall portion 136 of the airbag cover 132 so as to retainthe joint wall portion 136.

As shown in FIGS. 29 to 32, the retainer 117 is formed of a sheet metal,and includes a base 118 and a cover wall 121, as the retainer 17 in thefirst embodiment. The base 118 has an insert hole 119 opened generallyin the same shape as the insert hole 126 of the case 124. The cover wall121 extends up toward the airbag cover 132 from the outer peripheraledge of the base 118 in a generally square cylindrical shape.

The base 118 has a generally square outline, and is provided at twopositions out of its four corners with bolts 120 extended downward. Theremaining two corners are provided with retaining holes 118 a.

When the retainer 117 is arranged within the airbag 140, the individualbolts 120 are inserted into the mounting holes 146 of the airbag 140,the mounting holes 127 of the bottom wall 125 of the case 124, and therecesses 114 a of the flange 114 of the inflator 111, and are fastenedinto the nuts 116. Thus the airbag 140 and the inflator 111 are attachedto the bottom wall 125 of the case 124. In other words, when the bolts120 are fastened into the nuts 116, the peripheral edge 148 of theopening 145 of the airbag 140 is pressed onto the bottom wall 125 by thebase 118, thereby attaching the airbag 140 to the bottom wall 125, whilethe flange 114 of the inflator 111 is pressed onto the periphery of theinsert hole 126, thereby attaching the inflator 111 to the bottom wall125.

The individual retaining holes 118 a are disposed at the positionscorresponding to the insert holes 125 a of the bottom wall 125 of thecase 124 and the mounting holes 150 of the airbag 140, and are opened inthe same shape as those. That is, each of the retaining holes 118 a is acombination of a large hole 118 b which the neck 114 e and the head 114f of the retaining pawl 114 c of the inflator 111 can go through, and asmall hole 125 c communicating with the large hole 118 b. The neck 114 eof the retaining pawl 114 c can go through the small hole 118 c, but thehead 114 f of the retaining pawl 114 c cannot go through the small hole118 c in the vertical direction.

The cover wall 121 of the retainer 117 is extended upward toward theairbag cover 132 from the generally square outer circumferential edge ofthe base 118. The leading end 121 a of the cover wall 121 is extended upto the same level as the top surface 112 c of the inflator 111. Theleading end 121 a is not arranged at the four corners 121 b of the coverwall 121. At the corners 121 b, there are arranged recesses 122 recessedfrom the upper end 121 a to separate the upper end 121 a of the coverwall 121.

As the guide wall 21 in the first embodiment, the cover wall 121 coversthe gas discharge ports 113, with the upper end 121 a extended up to thesame level as the top surface 112 c of the inflator 11, so that the mistD contained in the inflation gas G discharged from the gas dischargeports 113 of the inflator 111 may adhere thereon. The recesses 122 inthe individual corners 121 b of the cover wall 121 constitute a throughportion penetrating the cover wall 121, and further constitute a mistgrowth prevention means B1 for preventing the mist D from forming mistagglomerates.

Here, the retainer 117 is formed by punching the insert hole 119,mounting holes for the bolts 120, the retaining holes 118 a, and therecesses 122 in a sheet metal, by drawing it to form the base 118 andthe cover wall 121, and by assembling the bolts 120.

The inflator 111 is a pyro-type inflator, which generates inflation gasby burning reaction of a predetermined gas generating material, forexample, a gas generating material composition containing by weight ofthe material 34% nitroguanidine, 50% nitrate strontium, 9% sodium saltof carboxymethylcellulose, and 7% acid clay. As shown in FIGS. 29 to 32,the inflator 111 is a disc-type including a body 112 of a generallycylindrical shape, and is a single type having one combustion chamber,and its gas discharge amount is 2.4 mol. Moreover, the inflator 111 is along mass flow type drawing a mass flow curve as shown in FIG. 20. Asthe inflator 11 in the first embodiment, in the inflator 111 in thesecond embodiment, although the mass flow rate of the inflation gas issmall right after the ignition, it increases from 30 msec after ignitionon, compared with a conventional inflator. Therefore, the airbag 140inflated by the inflation gas from the inflator 111 is able to protect apassenger in the front passenger's seat properly.

The inflator 111 includes a body 112 charged with a predetermined amountof gas generating material and a flange 114 for attaching the inflator111 to the case 124.

The flange 114 has a generally square annular shape (generally squareplate shape) projected from the outer circumference of the body 112. Itis provided at its four corners with each two of recesses 114 a andretaining pawls 114 c.

The individual recesses 114 a have a curved hook-like shape so that thebolts 120 of the retainer 117 may be inserted therein from the outerperipheral edge of the flange 114 when fitting the center of the body112 to the center of the insert hole 119 of the retainer 117 and turningclockwise as in FIGS. 34A and 34B. The width W0 of the individualrecesses 114 a is slightly greater than the outer diameter of the bolts120 (refer to FIG. 33).

Each of the retaining pawl 114 c includes a base 114 d extendingoutwardly from the flange 114, a neck 114 e extending up toward the gasdischarge ports 113 from the leading end of the base 114 d, and a head114 f extending outwardly from the upper end of the neck 114e. When theinflator 111 is assembled with the bottom wall 125 of the case 124, theinflator body 112 is inserted into the insert hole 126 of the casebottom wall 125, the opening 145 of the airbag 140, and the insert hole119 of the retainer 117 from the lower side. At this time, each of theheads 114 f and the necks 114 e of the retaining pawls 114 c is insertedinto the large holes 125 b, 150 a and 118 b, respectively of the inserthole 125 a of the bottom wall 125, the mounting hole 150 of the airbag140, and the retaining hole 118 a of the retainer 117, so that the head114 f is protruded above the upper surface of the base 118 of theretainer 117. Subsequently when the inflator body 112 is turnedclockwise as shown in FIGS. 34A and 34B with its center fitted to thecenter of the insert hole 119 of the retainer 117, the neck 114 e shiftsto the small holes 125 c, 150 b, and 118 c, respectively of the inserthole 125 a of the bottom wall 125, the mounting hole 150 of the airbag140, and the retaining hole 118 a of the retainer 117, so that the head114 f abuts against the peripheral edge of the small hole 125 c on theupper surface of the base 118 of the retainer 117. While the necks 114 eof the retaining pawls 114 c shift from the large hole 118 b to thesmall hole 118 c, the individual bolts 120 are inserted into theaforementioned recesses 114 a. By fastening the nuts 116 with theindividual bolts 120 as shown in FIGS. 34B, 35, 36 and 37, theindividual nuts 116 hold the peripheral edge 114 b of the recesses 114a, so that the inflator 111 is attached to the bottom wall 125 of thecase 124. The base 118 of the retainer 117, in cooperation with the nuts116 and the retaining pawls 114 c of the inflator 111, presses theopening peripheral edge 148 of the airbag 140 onto the bottom wall 125,thereby to be attached to the bottom wall 25 of the case 124.

The body 112 has a cylindrical shape whose outer diameter is slightlysmaller than the internal diameter of the insert hole 126 of the bottomwall 125. The body 112 is provided on the outer circumferential side 112b of the upper body 112 a above the flange 114 with a plurality of gasdischarge ports 113 for discharging the inflation gas G.

FIGS. 38 to 41 illustrate the airbag 140 of the second embodiment. Asthe airbag 40 of the first embodiment, the airbag 140 has, as completelyexpanded and inflated, a generally square conical shape and includes apassenger's side wall 140 a to be arranged generally in the verticaldirection and closer to the passenger, and a side wall portion 140 bextended toward the vehicle's front side from the outer peripheral edgeof the passenger's sidewall 140 a in a narrowing manner. In the frontlower side of the side wall portion 140 b, there is arranged a roundopening for admitting the inflation gas, or the gas inlet port 145. Inthe periphery of the gas inlet port 145, there are formed each two ofthe mounting holes 146 and 150. The upper portion 112 a of the inflatorbody 112 is inserted into the gas inlet port 145. The individualmounting holes 146 receive the individual bolts 120 of the retainer 117.

As shown in FIGS. 33, 34 and 37, the individual mounting holes 150 aredisposed at the positions corresponding to the retaining holes 118 a ofthe retainer 117 and the insert holes 125 a of the case bottom wall 125,and are opened in the same shape as those. That is, each of the mountingholes 150 is a combination of a large hole 150 a which the neck 114 eand the head 114 f of the retaining pawl 114 c of the inflator 111 cango through, and a small hole 150 b communicating with the large hole 150a. The neck 114 e of the retaining pawl 114 c can go through the smallhole 150 b, but the head 114 f of the retaining pawl 114 c cannot gothrough the small hole 150 b in the vertical direction. The airbag 140is further provided in the left and right side of the side wall portion140 b respectively with a vent hole 147 for emitting extra inflationgas.

As shown in FIGS. 40 and 41, the airbag 140 is formed of four clothmembers: a first base cloth 141, a second base cloth 142, a commutatorcloth 143 and a reinforcing cloth 144, as the airbag 40 of the firstembodiment. These cloths are formed of a plain woven fabric of syntheticfiber yarn such as polyamide or the like without heat-resisting coating.The capacity of the airbag 140 is 110 l, too, as in the firstembodiment.

The first base cloth 141 is shaped like a combination of two generallyhexagonal portions, i.e., the upper portion 141 a and the lower portion141 e, and the second base cloth 142 has a generally round shapeapproximate to a generally hexagonal shape. As in the first embodiment,these planar base cloths 141 and 142 are also constructed to provide thesolid airbag 140 by sewing work. The second base cloth 142 constitutesthe generally entire area of the passenger's side wall 140 a of theairbag 140, and the first base cloth 141 constitutes the generallyentire area of the side wall portion 140 b of the airbag 140. Moreover,the upper portion 141 a of the first base cloth 141 constitutes thegenerally entire area of the upper side of the side wall portion 140 b,whereas the lower portion 141 e of the first base cloth 141 constitutesthe generally entire area of the lower side of the side wall portion 140b.

The reinforcing cloth 144 is stitched to the periphery 148 of the gasinlet port 145 at the inner side of the airbag 140 to protect the firstbase cloth 141. The commutator cloth 143 is arranged inside the airbag140 to cover the gas inlet port 145, and guides the inflation gasflowing in the airbag 140 toward the vehicle's front and reardirections.

The commutator cloth 143 also covers the periphery 148 of the gas inletport 145 in the first base cloth 141, and therefore, the part 143 dreinforces the base cloth 141. More specifically, the part 143 d of thecommutator cloth 143 and the reinforcing cloth 144 function as aprotection cloth member 151 for covering the inner side of the periphery148 of the opening (or the gas inlet port) 145 in the first base cloth141 as a part of the airbag 140. These cloths cover the part 149 of theinner side of the airbag 140 neighboring the opening peripheral edge 148at least up to the area over the upper end 121 a of the cover wall 121of the retainer 117.

To manufacture the airbag 140, as the airbag 40 in the first embodiment,the reinforcing cloth 144 and the commutator cloth 143 are firstlystitched to the to-be inner side of the first base cloth 141 at theopening peripheral edge 148 of the gas inlet port 145 by the stitchingyarn S, as shown in FIGS. 40 and 41A. As shown in FIG. 41B,subsequently, the ends of the commutator cloth 143 are stitched uptogether by the stitching yarn S, thereby to form the predeterminedshape of the commutator cloth 143. Here in the second embodiment, too,the first base cloth 141 has been provided with the vent holes 147, thegas inlet port 145 and the mounting holes 146 and 150 in advance, whilethe commutator cloth 143 and the reinforcing cloth 144 has been providedwith the gas inlet port 145 and the mounting holes 146 and 150 inadvance, as in the first embodiment. However, the vent-holes 147, thegas inlet port 145 and the mounting holes 146 and 150 may be formedafter the reinforcing cloth 144 and the commutator cloth 143 arestitched to the first base cloth 141.

As shown in FIGS. 41B and 41C, thereafter, the first base cloth 141 isfolded back on the first base line X1 extending in the transversedirection between the upper portion 141 a and the lower portion 141 e.Then the straight edges 141 b and 141 f of the upper and lower portions141 a and 141 b, respectively, near the first base line X1 are stitchedup together, and the other straight edges 141 c and 141 g are stitchedup together, too.

Subsequently as shown in FIGS. 41C and 41D, the upper portion 141 a isfolded back on the second base line X2 extending between the portionsprojected in the transverse directions, so that the unstitchedperipheral edges 141 d and 141 h of the upper and lower portions 141 aand 141 e are separated and developed flatly. The outer shape in thisexpanded state is the same as the outer shape of the second base cloth142.

Then as shown in FIGS. 41D and 41E, the second base cloth 142 is appliedhereon, and the individual outer peripheral edges are stitched uptogether by the stitching yarn S. Thus the airbag 140 is formed into abag shape so that the stitch margin may not appear on the outer surface.

Thereafter, the airbag 140 is reversed inside out utilizing the gasinlet port 145.

The mounting of the airbag 140 thus manufactured on the vehicle isstarted by placing the retainer 117 inside of the airbag 140 so that thebolts 120 maybe protruded from the mounting holes 146, and then foldingthe airbag 140. Then the folded airbag 140 is wrapped by a breakablewrapping sheet 139 (refer to FIG. 30) to keep the folded-up state.

Then, the folded airbag 140 is located on the bottom wall 125 of thecase 124 from the opening 124 a by inserting the individual bolts 120into the mounting holes 127 from above. Subsequently, the upper portion112 a of the body 112 of the inflator 111 is inserted into the inserthole 126, the airbag opening 145, and the insert hole 119 from the lowerside. At this time, as shown in FIGS. 33 and 34A, the heads 114 f andthe necks 114 e of the individual retaining pawls 114 c of the inflator111 are inserted into the large holes 125 b, 150 a and 118 b of theinsert holes 125 a of the bottom wall 125, the mounting holes 150 of theairbag 140, and the retaining holes 118 a of the retainer 117, so thatthe heads 114 f are protruded on the upper surface of the base 118 ofthe retainer 117. Then the inflator body 112 is turned clockwise, asshown in FIGS. 34A and 34B, to shift the necks 114 e to the small holes125 c, 150 b and 118 c of the insert holes 125 a of the bottom wall 125,the mounting holes 150 of the airbag 140, and the retaining holes 118 aof the retainer 117, so that the heads 114 f come to abut against theperipheral edge of the small hole 118 c on the upper surface of the base118 of the retainer 117, as shown in FIG. 37. At this time, theindividual bolts 120 are inserted into the recesses 114 a of theinflator 111. If the nuts 116 then are fastened to the bolts 120, thenuts 116 hold the peripheral edge 114 b of the recesses 114 a to attachthe inflator 111 to the bottom wall 125 of the case 124. The base 118 ofthe retainer 117, in cooperation with the nuts 116 and the retainingpawls 114 c of the inflator 111, presses the opening peripheral edge 148of the airbag 140 onto the bottom wall 125, thereby to be attached tothe bottom wall 25 of the case 124.

Thereafter, the side wall 129 of the case 124 is inserted within thejoint wall portion 136 of the airbag cover 132 in the dashboard 1mounted on the vehicle, and the individual retaining pawls 130 of thecase 124 are inserted into the retaining holes 137 on the joint wallportion 136. Thus the retaining pawls 130 are retained by the joint wallportion 136. If the bolts 9 are fastened into the nuts 128 a of theindividual brackets 128 through the mounting seats 8 a, the airbagdevice M2 for front passenger's seat is mounted on the vehicle.

Alternatively, as in the first embodiment, the mounting of the airbagdevice M2 on the vehicle may also be made by assembling the case 124with the airbag 140 and the inflator 111 to the airbag cover 132 of thedashboard 1, and securing this airbag device M2 to the body 6 with thebolts 9 when attaching the dashboard 1 to the vehicle.

After mounting the airbag device M2 on the vehicle, when the inflationgas G is discharged from the individual gas discharge ports 113 of theinflator 111, the airbag 140 inflates and breaks the wrapping sheet 139.The airbag 140 further breaks the breakable portion 135 and opens thedoors 133F and 133B of the airbag cover 132 as indicated by thedouble-dotted lines in FIGS. 29 and 30, and then protrudes from theopening 138 provided by the doors 133F and 133B.

The airbag 140 thus completes the inflation, and emits the extra gasfrom the vent holes 147.

Since the airbag device M2 of the second embodiment employs the inflator111 of pyro- and long mass flow type, the inflator 111 is compact, andis able to expand and inflate the airbag 140 for front passenger's seatproperly.

In the airbag device M2 of the second embodiment, even if the inflationgas G containing the mist D is discharged from the gas discharge ports113 of the inflator 111 when the airbag 140 inflates, the mist D adheresto the cover wall 121, as shown in FIG. 42, and does not grow to formlarge mist agglomerates because of the mist growth prevention means B1.

In the second embodiment, more specifically, the cover wall 121 of theretainer 117 is arranged in a generally square cylindrical shapeencircling the end portion 112 a of the inflator 111 having gasdischarge ports 113. Moreover, at the four corners 121 b of the coverwall 121, there are arranged recesses 122 as a through portion recessedfrom the leading end 121 a of the cover wall 121 to form the mist growthprevention means

In the cover wall 121 of a generally square cylindrical shape encirclingthe inflator 111, the mist D is likely to gather to form mistagglomerates at the four corners 121 b. With the construction of thesecond embodiment, however, even if the mist D gathers in the corners121 b, it is blown off from the recesses 122 before formingagglomerates, and does not form big mist agglomerates.

In the airbag device M2 for front passenger's seat of the secondembodiment, therefore, even if the inflation gas G discharged from theinflator 111 contains a lot of mist D, the mist D does not form mistagglomerates.

It is desired that the width Y (refer to FIG. 32) of the through portion122 in the corners 121 b of the cove wall 121 be 5 to 15 mm. Under 5 mm,it is difficult for the mist D to go out of the cover wall 121, and over15 mm, it is difficult for the mist D to adhere to the cover wall 121.The length Z of the through portion 122 is desirably 10 to 15 mm. Under10 mm, it is difficult for the mist D to go out of the cover wall 121,and over 15 mm, it is difficult for the mist D to adhere to the coverwall 121.

In the second embodiment, moreover, the cover wall 121 of the retainer117 is arranged to protect the part 149 of the airbag 140 neighboringthe opening peripheral edge 148 held by the base 118 of the retainer 117from the gas discharge ports 113 of the inflator 111. Therefore, thecover wall 121 prevents the high temperature inflation gas G containingthe high temperature mist D from hitting directly the part 149 of theairbag 140 neighboring the opening peripheral edge 148 as much aspossible, and contributes to the protection of the part 149 of theairbag 140 neighboring the opening peripheral edge 148 from heat.

Especially in the second embodiment, the airbag 140 is provided at theinner side of its opening peripheral edge 148 with a protection clothmember 151 (144 and 143 d) for protecting the base cloth 141 up to thearea over the leading end 121 a of the cover wall 121 of the retainer117 in the completely inflated airbag 140. With this construction, whenthe mist D flows out of the cover wall 121 toward the part 149 of theairbag 140 neighboring the opening peripheral edge 148, it adheres tothe protection cloths 144 and 143 d in the inner side of the base cloth141. Therefore, the mist D is prevented from adhering to the base cloth141 constituting the bag shape, or the outer shape of the airbag 140.

The mist growth prevention means may be constructed as shown in FIGS. 43and 44. The mist growth prevention means B2 shown in FIGS. 43 and 44 isformed by providing numbers of through holes 121 c on the cover wall121A of the retainer 117 instead of providing the recess 122. In theillustrated embodiment, the internal diameter d of each of theindividual through holes 121 c is 2 mm, and the pitch P between theneighboring through holes 121 c is 5 mm. The upper end 121 a of thecover wall 121A extends from the base 118 up to the same level as thetop surface 112 c of the inflator 111, as in the cover wall 121.

With this construction, the mist D from the gas discharge ports 113 goesout of the through holes 121 c before further growth, or adheres to theperipheral edge of the through holes 121 c in the cover wall 121A. Themist D adhered to the peripheral edge of the through holes 121 c isprevented from forming mist agglomerates since the mist D continues togo out of the through holes 121 c and little mist D follows to adherethereto.

Even if it grows to form mist agglomerates, the agglomerates are likelyto adhere to the inner circumference of the through holes 121 c whichare great in number, and the agglomerates are hardly blown off into theairbag 140. Therefore, it is prevented that the big mist agglomeratesadhere to the base cloths 141 and 142.

It is desired that the internal diameter d of each of the through holes121 c is 1 to 3 mm, and the pitch P of forming the through holes 121 cis 5 to 10 mm. If the internal diameter d is under 1 mm, it is difficultfor the mist D to go out of the cover wall 121A, and if the internaldiameter d is over 3 mm, it is difficult for the mist D to adhere to thecover wall 121A. If the pitch P is under 5 mm, it is difficult for themist D to adhere to the cover wall 121A, and if the pitch P is over 10mm, it is difficult for the mist D to go out of the cover wall 121A.

The cover wall 121A may have recesses 122 at the corners 121 b as in thecover wall 121.

Furthermore, the mist growth prevention means may be constructed asshown in FIGS. 45 and 46. The mist growth prevention means B3 is formedby a cover wall 121B of the retainer 117A including tongue pieces 121 dso arranged separate from one another as to confront the individual gasdischarge ports 113 of the inflator 111. The upper ends 121 a of theindividual tongue pieces 121 d extend from the generally annular base118 up to the same level as the top surface 112 c of the inflator 111,as in the cover wall 121.

With this construction, the mist D from the individual gas dischargeports 113 adheres to the tongue piece 121 d covering the respective gasdischarge port 113. The mist D from other gas discharge ports 113 thanthe confronting port 113 hardly adheres to the respective tongue piece121 d. Accordingly, the forming of mist agglomerates is prevented.Moreover, the tongue pieces 121 d are provided with spaces 123 inbetween the neighboring tongue pieces 121 d, and great deal of theinflation gas G from the gas discharge ports 113 flows toward the spaces123. Therefore, the mist D adhered to the individual tongue pieces 121 dis likely to be blown off toward the spaces 123 between the tonguepieces 121 d before growing to form mist agglomerates.

It is desired that the individual tongue pieces 121 d confronting theindividual gas discharge ports 113 have its width W1 corresponding tothe angular range of the inflation gas G discharged from the gasdischarge ports 113 as reaching the tongue piece 121 d.

Irrespective of forming the mist growth prevention means by the throughholes 121 c or the tongue pieces 121 d of the cover walls 121A and 121B,as shown in FIGS. 43 to 46, the base cloth 141 of the airbag 140 isprovided at the inner side of the part 149 neighboring the openingperipheral edge 148 with the protection cloths 144 and 143 d. Therefore,even if the mist D passes through the through holes 121 c or the spaces123 between the tongue pieces 121 d out of the cover walls 121A and121B, and flows toward the part 149 neighboring the opening peripheraledge 148, it adheres to the protection cloths 144 and 143 d at the innerside of the base cloth 141. Consequently, the adhesion of the mist D tothe base cloth 141 constituting the outer shape of the airbag 140 isprevented.

Here in the airbag 140 of the second embodiment upon the inflation, inthe inner side away from the top surface 1 a of the dashboard 1, theinflation gas G is guided toward the vehicle's front and rear sides bythe commutator cloth 143 to expand the airbag 140 widely in thevehicle's longitudinal direction. Then the airbag 140 completes theinflation while bringing the passenger's side wall 140 a close to thevertical face toward the passenger. Since the airbag 140 is able torestrain the passenger with the flat and wide passenger's side wall 140a expanded generally vertically, it does not apply a partial pressure tothe passenger. Here, the vicinity of the transverse center 143 c of thecommutator cloth 143 is so arranged in the airbag 140 as to be disposedabove the top surface 1 a of the dashboard 1 when the airbag 140 isinflated (refer to FIGS. 29 and 39).

In the second embodiment, moreover, as shown in FIG. 39, the reinforcingcloth 144 is extended in the front and rear sides so as to confront theopening 143 a and 143 b of the commutator cloth 143 guiding the gas Gtoward the front and rear sides when the airbag 140 inflates. Even ifthe mist before forming mist agglomerates passes over the cover wall 121and flows into the airbag 140, it is captured by the commutator cloth143 firstly and hardly contacts the first base cloth 141 and the secondbase cloth 142 directly. Even if the mist is contained in the inflationgas G directed toward the front and rear directions by the commutatorcloth 143, the reinforcing cloth 144 captures the mist.

In the second embodiment, the cover wall 121 of the retainer 117 isarranged in a generally square cylindrical shape encircling the body 112of the inflator 111. However, the cover wall 121 may be formed in agenerally cylindrical shape encircling the inflator body 112, as thecover wall 121B shown in FIG. 45.

The smallest clearance L between the gas discharge port 113 and thecover wall 121 (refer to FIG. 46) is desirably set within the range of 8to 20 mm. If it is under 8 mm, the cover wall 121 is prone to bedeformed, thereby making difficult for the mist D to adhere thereto.Even if the cover wall 121 is not deformed, the pressure loss of the gasG is increased, so that it takes the airbag 140 more time to be inflatedcompletely. If the clearance L is over 20 mm, it is too far for the mistD to adhere to the cover wall 121, so that the meaning of providing thecover wall 121 is lost.

In the airbag device M2 in the second embodiment, the two bolts 120 ofthe retainer 117 and the two retaining pawls 114 c of the inflator 111are employed for the attachment of the airbag 140 and the inflator 111to the bottom wall 125 of the case 124. In comparison with the casehaving four bolts 120 at the positions of the retaining holes 118 a ofthe retainer 117 to attach the airbag 140 and the inflator 111 to thebottom wall 125 of the case 124, the detachment of the inflator 111 inscrapping can be done easily in the airbag device M2 since fewer bolts120 are used.

Especially in the second embodiment, the two bolts 120 are arranged inthe side closer to the not-shown glove box at the rear side of the case124. Therefore, the detachment of the nuts 116 can be done easily,thereby further facilitating the detachment work of the inflator 111 inscrapping.

In the second embodiment, the airbag cover 132 is formed integral withthe dashboard 1. However, the airbag cover 132 may be formed separatelyfrom the dashboard 1.

1. An airbag device for a front passenger's seat mounted on theinstrument panel in front of the front passenger's seat, comprising: anairbag to be inflated upon the inflow of the inflation gas, whose gaspermeability rate is 1.0 l/cm²/min or under at 20 kPa air pressure, andwhose weight is 230 g/m² or under; and an inflator for generating theinflation gas and supplying the airbag with the inflation gas, the gasbeing generated by a chemical reaction and in which a mass flow curvearea thereof from 30 ms after the ignition of the inflator occupies morethan 25% of the entire area of the mass flow curve wherein in the headdeceleration in a decision area of 55 to 75 ms is 100 m/s² or above whentested frontal collision FRB (Full Rap Barrier) test according to FMVSSNo. 208-66FR65403 effective on May 28, 2003, conducted at 20 to 25 MPHon an unbelted passenger dummy, the head deceleration in a decision areaof 55 to 75 sec is 100 m/s² or above, wherein: the airbag: includes agas inlet port for admitting the inflation gas, and is folded and housedin a case, and pushes and opens the doors arranged in the instrumentpanel upon the inflow of the inflation gas from the gas inlet port toexpand and inflate toward a vehicle's rear side; as the shape ascompletely expanded and inflated, a passenger's side wall to be arrangedgenerally along the vertical direction and closer to a passengerposition, and a side wall portion extended toward a vehicle's front sidefrom the outer peripheral edge of the passenger's side wall whilenarrowing in a generally conical shape; is provided at the front lowerside of the side wall portion as completely inflated with the gas inletport arranged generally horizontally, the peripheral edge of the gasinlet port being attached to the case; and is housed in the case afterbeing folded through a preliminary folding step firstly, and thenthrough a transverse folding step and a vertical folding step; and thepreliminarily folded shape of the airbag is flat with part near theupper edge of the passenger's side wall disposed in a positionconfronting the gas inlet port, and with the remainder of thepassenger's side wall overlapped with the lower part of the side wallportion as inflated.
 2. An airbag device for a front passenger's seataccording to claim 1, wherein the generally entire area of thepassenger's side wall is flatly expanded while the side wall portion isfolded when the preliminary folding of the airbag is completed.
 3. Anairbag device for a front passenger's seat according to claim 2, whereinthe upper part of the gas inlet port in the side wall portion is foldedand disposed in the range from the vicinity of the rear edge of the gasinlet port toward the front side.